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Renal I > Mechanisms to Adjust Urine Concentration - McCormick > Flashcards

Mechanisms to Adjust Urine Concentration - McCormick Flashcards

1
Q

Na reabsorption in PT

A

50-55%
Na/H exchanger
Cotransport with glucose, AA, phosphate

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2
Q

Na reabsorption in TAL

A

35-40%
Na/K/2Cl
Impermeable to water

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3
Q

Na reabsorption in DCT

A

5-8%

Na/Cl cotransporter

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4
Q

Na reabsorption in Late DCT/CD

A

2-3%

Luminal Na+ membrane channels

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5
Q

Chloride reabsorption

A

Always linked either directly or indirectly to Na reabsorpton

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6
Q

Descending loop of Henle

A

Freely permeable to water

Impermeable to Na+, Cl-

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7
Q

Transport in first half of DCT

A 
Tubular urine:
Na/Cl
K/Cl
Blood side:
Na/K
K leak
Cl leak
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8
Q

What is the major site of physiological control of salt and water balance?

A

Late DCT/CD

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9
Q

What hormones control salt and water balance?

A

Aldosterone - Na reabsorption, K and H secretion
ANP - Inhibits Na reabsorption
ADV - water reabsorption

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10
Q

What is the driving force for K and H secretion by the principal cells?

A

The large transepithelial potential

-50 mV, lumen negative

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11
Q

How does Aldosterone increase Na reabsorption in principal cells

A

Incorporation of Na channels in luminal membrane

Incorporation of Na/K ATPase in basolateral membrane

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12
Q

How does ADH increase H2O permeability in Late DCT/CD?

A

Via V2 receptors and insertion of aquaporin channels

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13
Q

Countercurrent multiplier mechanism

A

Concentrates solute in medullary interstitium

High solute conc enables kidney to excrete high conc urine

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14
Q

How does urea get concentrated in inner medulla?

A

ADH promotes reabsorption form inner medullary CD

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15
Q

Describe urine in antidiuresis

A

Low volume, high urine concentration

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16
Q

Describe urine in diuresis

A

High volume of dilute urine is excreted

17
Q

Talk to me about obligatory urine volume

A

The body generates 600 mOsm waste/day
Can concentrate to 1200 mOsm
SO…. minimum to remove waste is 0.5 L/day

18
Q

Osmolar clearance

A

Uosm x V/Posm

19
Q

Free water clearance

A

Excretion of water in excess of amount needed to excrete isosmotic urine

20
Q

If Uosm < Posm is positive

A

Pure water is cleared from body

21
Q

If Uosm > Posm is negative

A

Pure water is retained

22
Q

Fractional excretion

A

The fraction (percentage) of the filtered load of a substance that is secreted in urine

UP/PU
(Na is first, cr second)

23
Q

Fractional excretion < 1%

A

Pre renal and AGN

Na avidly reabsorbed

24
Q

Fractional excretion > 2%

A

ATN, Renal

Renal I (20 decks)

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